Systems theory is an interdisciplinary field of science and the study of the nature of complex systems in nature, society, and science. More specificially, it is a framework by which one can analyze and/or describe any group of objects that work in concert to produce some result. This could be a single organism or an ecosystem, any organization or society, or any electro-mechanical or informational artifact. Systems concepts predominantly refer to the science of systems that resulted from Bertalanffy's General System Theory (GST), among others, in initiating what became a project of systems research and practice. It has long been used in sociology and biology and the area is often associated with cybernetics. Margaret Mead and Gregory Bateson developed interdisciplinary perspectives in systems theory (such as positive and negative feedback in the social sciences) and recognized the applicability of systems theory to social relations (individuals) and social systems (cultures).

In this respect, with the possibility of misinterpretations, Bertalanffy [1] believed a general theory of systems “should be an important regulative device in science,” to guard against superficial analogies that “are useless in science and harmful in their practical consequences.” Others remain closer to the direct systems concepts developed by the original theorists. For example, Ilya Prigogine, of the Center for Complex Quantum Systems at the University of Texas, Austin, has studied emergent properties, suggesting that they offer analogues for living systems. The theories of Autopoiesis of Francisco Varela and Humberto Maturana are a further development in this field. Important names in contemporary systems science include Russell Ackoff, Bela Banathy, Stanford Beer, Mandy Brown, Peter Checkland, Robert Flood, Fritjof Capra, Michael C. Jackson, and Werner Ulrich, among others.
With the modern foundations for a general theory of systems following the World Wars, Ervin Laszlo, in the preface for Bertalanffy's book Perspectives on General System Theory, maintains that the translation of "general system theory" from German into English has "wroth a certain amount of Havoc" [2]. The preface explains that the original concept of a general system theory was "Allgemeine Systemtheorie (or Lehre)," pointing out the fact that "Theorie" (or "Lehre") just as "Wissenschaft" (translated Scholarship), "has a much broader meaning in German than the closest English words ‘theory’ and ‘science'" [3]. With these ideas referring to an organized body of science and "any systematically presented set of concepts, whether they are empirical, axiomatic, or philosophical," "Lehre" is associated with theory and science in the etymology of general systems, but also does not translate from the German very well; "teaching" is the closest equivalent [4]. While many of the root meanings for the idea of a “general systems theory” might have been lost in the translation and many were led to believe that the theorists had articulated nothing but a pseudoscience, systems theory became a nomenclature that early investigators used to describe the interdependence of relationships in organization by defining a new way of thinking about science and scientific paradigms.

A system from this frame of reference is composed of regularly interacting or interrelating groups of activities. For example, in noting the influence in organizational psychology as the field evolved from “an individually oriented industrial psychology to a systems and developmentally oriented organizational psychology,” it was recognized that organizations are complex social systems; reducing the parts from the whole reduces the overall effectiveness of organizations [5]. This is at difference to conventional models that center on individuals, structures, departments and units separate in part from the whole instead of recognizing the interdependence between groups of individuals, structures and processes that enable an organization to function. Laszlo [6] explains that the new systems view of organized complexity went "one step beyond the Newtonian view of organized simplicity" in reducing the parts from the whole, or in understanding the whole without relation to the parts. The relationship between organizations and their environments became recognized as the foremost source of complexity and interdependence. In most cases the whole has properties that cannot be known from analysis of the constituent elements in isolation. Bela H. Banathy, who argued - along with the founders of the systems society - that “the benefit of humankind” is the purpose of science, has made significant and far-reaching contributions to the area of systems theory. For the Primer Group at ISSS, Banathy defines a perspective that iterates this view:

The systems view is a world-view that is based on the discipline of SYSTEM INQUIRY, Central to systems inquiry is the concept of SYSTEM. In the most general sense, system means a configuration of parts connected and joined together by a web of relationships. The Primer group defines system as a family of relationships among the members acting as a whole. Bertalanffy defined system as "elements in standing relationship." [7]

Similar ideas are found in learning theories that developed from the same fundamental concepts, emphasizing that understanding results from knowing concepts both in part and as a whole. In fact, Bertalanffy’s organismic psychology paralleled the learning theory of Jean Piaget (Bertalanffy 1968). Interdisciplinary perspectives are critical in breaking away from industrial age models and thinking where history is history and math is math segregated from the arts and music separate from the sciences and never the twain shall meet [8]. The influential contemporary work of Peter Senge [9] provides detailed discussion of the commonplace critique of educational systems grounded in conventional assumptions about learning, including the problems with fragmented knowledge and lack of holistic learning from the "machine-age thinking" that became a "model of school separated from daily life." It is in this way that systems theorists attempted to provide alternatives and an evolved ideation from orthodox theories with individuals such as Max Weber, Emile Durkheim in sociology and Frederick Winslow Taylor in scientific management, which were grounded in classical assumptions [10]. The theorists sought holistic methods by developing systems concepts that could be integrated with different areas.

The contradiction of reductionism in conventional theory (which has as its subject a single part) is simply an example of changing assumptions. The emphasis with systems theory shifts from parts to the organization of parts, recognizing interactions of the parts are not "static" and constant but "dynamic” processes. Conventional closed systems were questioned with the development of open systems perspectives. The shift was from absolute and universal authoritative principles and knowledge to relative and generalconceptual and perceptual knowledge [11], still in the tradition of theorists that sought to provide means in organizing human life. Meaning, the history of ideas that preceded were rethought not lost. Mechanistic thinking was particularly critiqued, especially the industrial-age mechanistic metaphor of the mind from interpretations of Newtonian mechanics by Enlightenment philosophers and later psychologists that laid the foundations of modern organizational theory and management by the late 19th century [12]. Classical science had not been overthrown, but questions arose over core assumptions that historically influenced organized systems, within both social and technical sciences.

Whether considering the first systems of written communication with Phoeniciancuneiform to Mayan numerals, or the feats of engineering with the Egyptian pyramids, systems thinking in essence dates back to antiquity. Differentiated from Western rationalist traditions of philosophy, C. West Churchman often identified with the I Ching as a systems approach sharing a frame of reference similar to pre-Socratic philosophy and Heraclites[13]. Bertalanffy traced systems concepts to the philosophy of G.W. von Leibniz and Nicholas of Cusa’s Coincidentia Oppositorum. While modern systems are considerably more complicated, today’s systems are embedded in history.

Systems theory as an area of study specifically developed following the World Wars from the work of Ludwig von Bertalanffy, Anatol Rapoport, Kenneth E. Boulding, William Ross Ashby, Margaret Mead, Gregory Bateson, C. West Churchman and others in the 1950s, specifically catalyst from the Macy conferences. Cognizant of advances in science that questioned classical assumptions in the organizational sciences, Bertalanffy's idea to develop a theory of systems began as early as the interwar period, publishing "An Outline for General Systems Theory" in the British Journal for the Philosophy of Science, Vol 1, No. 2, by 1950. Where assumptions in Western science from Greek thought with Plato and Aristotle to Newton’s Principia have historically influenced all areas from the social to hard sciences, the original theorists explored the implications of twentieth century advances in terms of systems.

The systems view was based on several fundamental ideas. First, all phenomena can be viewed as a web of relationships among elements, or a system. Second, all systems, whether electrical, biological, or social, have common patterns, behaviors, and properties that can be understood and used to develop greater insight into the behavior of complex phenomena and to move closer toward a unity of science. System philosophy, methodology and application are complementary to this science [14]. By 1956, the Society for General Systems Research was established, renamed the International Society for Systems Science in 1988. The Cold War had its affects upon the research project for systems theory in ways that sorely disappointed many of the seminal theorists. Some began to recognize theories defined in association with systems theory had deviated from the initial General Systems Theory (GST) view (Hull 1970). The economist Kenneth Boulding, an early researcher in systems theory, had concerns over the manipulation of systems concepts. Boulding concluded from the effects of the Cold War that abuses of power always prove consequential and that systems theory might address such issues [15]. Since the end of the Cold War, there has been a renewed interest in systems theory with efforts to strengthen an ethical view.

Many early systems theorists aimed at finding a general systems theory that could explain all systems in all fields of science. The term goes back to Bertalanffy's book titled General System Theory. von Bertalanffy's objective was to bring together under one heading the organismic science that he had observed in his work as a biologist. His desire was to use the word "system" to describe those principles which are common to systems in general. In GST, he writes:

...there exist models, principles, and laws that apply to generalized systems or their subclasses, irrespective of their particular kind, the nature of their component elements, and the relationships or "forces" between them. It seems legitimate to ask for a theory, not of systems of a more or less special kind, but of universal principles applying to systems in general.[16]

Ervin Laszlo [17] in the preface of von Bertalanffy's book Perspectives on General System Theory..[18]

Thus when von Bertalanffy spoke of Allgemeine Systemtheorie it was consistent with his view that he was proposing a new perspective, a new way of doing science. It was not directly consistent with an interpretation often put on "general system theory," to wit, that it is a (scientific) "theory of general systems." To criticize it as such is to shoot at straw men. Von Bertalanffy opened up something much broader and of much greater significance than a single theory (which, as we now know, can always be falsified and has usually an ephemeral existence): he created a new paradigm for the development of theories.

Ludwig von Bertalanffy outlines systems inquiry into three major domains: Philosophy, the Science, and Technology. In his work with the Primer Group, Bela H. Banathy generalized the domains into four integratable domains of systemic inquiry:

Cybernetics is the study of feedback and derived concepts such as communication and control in living organisms, machines and organisations. Its focus is how anything (digital, mechanical or biological) processes information, reacts to information, and changes or can be changed to better accomplish the first two tasks.

The terms "systems theory" and "cybernetics" have been widely used as synonyms. Some authors use the term cybernetic systems to denote a proper subset of the class of general systems, namely those systems that include feedback loops. However Gordon Pask's differences of eternal interacting actor loops (that produce finite products) makes general systems a proper subset of cybernetics. According to Jackson (2000), Bertalanffy promoted an embryonic form of general system theory (GST) as early as the 1920s and 1930s but it was not until the early 1950s it became more widely known in scientific circles.

Threads of cybernetics began in the late 1800s that led toward the publishing of seminal works (eg., Wiener’s Cybernetics in 1946 and von Bertalanffy’s General Systems Theory in 1968). Cybernetics arose more from engineering fields and GST from biology. If anything it appears that although the two probably mutually influenced each other, cybernetics had the greater influence. Bertalanffy (1969) specifically makes the point of distinguishing between the areas in noting the influence of cybernetics:

Systems theory is frequently identified with cybernetics and control theory. This again is incorrect. Cybernetics as the theory of control mechanisms in technology and nature and founded on the concepts of information and feedback, is but a part of a general theory of systems;” then reiterates: "the model is of wide application but should not be identified with 'systems theory' in general," and that "warning is necessary against its incautious expansion to fields for which its concepts are not made." (17-23).

Jackson (2000) also claims Bertalanffy was informed by Alexander Bogdanov’s three volume Tectology that was published in Russia between 1912 and 1917, and was translated into German in 1928. He also states it is clear to Gorelik (1975) that the “conceptual part” of general system theory (GST) had first been put in place by Bogdanov. The similar position is held by Mattessich (1978) and Capra (1996). Bertalanffy never even mentioned Bogdanov in his works, which Capra (1996) finds "surprising".

Cybernetics, catastrophe theory, chaos theory and complexity theory have the common goal to explain complex systems that consist of a large number of mutually interacting and interrelated parts in terms of those interactions. Cellular automata (CA), neural networks (NN), artificial intelligence (AI), and artificial life (ALife) are related fields, but they do not try to describe general (universal) complex (singular) systems. The best context to compare the different "C"-Theories about complex systems is historical, which emphasizes different tools and methodologies, from pure mathematics in the beginning to pure computer science now. Since the beginning of chaos theory when Edward Lorenz accidentally discovered a strange attractor with his computer, computers have become an indispensable source of information. One could not imagine the study of complex systems without the use of computers today.

Complex adaptive systems are special cases of complex systems. They are complex in that they are diverse and made up of multiple interconnected elements and adaptive in that they have the capacity to change and learn from experience. The term complex adaptive systems was coined at the interdisciplinary Santa Fe Institute (SFI), by John H. Holland, Murray Gell-Mann and others.

CAS ideas and models are essentially evolutionary, and they take ground in the modern biological views on adaptation and evolution. Accordingly, the theory of complex adaptive systems bridges developments of the system theory with the ideas of 'generalized Darwinism', which suggests that Darwinian principles of evolution are capable to explain a range of complex material phenomena, from cosmic to social objects.

Living systems theory is an offshoot of Bertalanffy's general systems theory, created by James Grier Miller, which was intended to formalize the concept of "life". According to Miller's original conception as spelled out in his magnum opus Living Systems, a "living system" must contain each of 20 "critical subsystems", which are defined by their functions and visible in numerous systems, from simple cells to organisms, countries, and societies. In Living Systems Miller provides a detailed look at a number of systems in order of increasing size, and identifies his subsystems in each.

James Grier Miller (1978) wrote a 1,102-page volume to present his living systems theory. He constructed a general theory of living systems by focusing on concrete systems—nonrandom accumulations of matter-energy in physical space-time organized into interacting, interrelated subsystems or components. Slightly revising the original model a dozen years later, he distinguished eight “nested” hierarchical levels in such complex structures. Each level is “nested” in the sense that each higher level contains the next lower level in a nested fashion.

The systems framework is also fundamental to organizational theory as organizations are complex dynamic goal-oriented processes. One of the early thinkers in the field was Alexander Bogdanov, who developed his Tectology, a theory widely considered a precursor of Bertalanffy's GST, aiming to model and design human organizations (see Mattessich 1978, Capra 1996). Kurt Lewin was particularly influential in developing the systems perspective within organizational theory and coined the term "systems of ideology", from his frustration with behavioral psychologies that became an obstacle to sustainable work in psychology [20]. Jay Forrester with his work in dynamics and management alongside numerous theorists including Edgar Schein that followed in their tradition since the Civil Rights Era have also been influential.

The systems approach to organizations relies heavily upon achieving negative entropy through openness and feedback. A systemic view on organizations is transdisciplinary and integrative. In other words, it transcends the perspectives of individual disciplines, integrating them on the basis of a common "code", or more exactly, on the basis of the formal apparatus provided by systems theory. The systems approach gives primacy to the interrelationships, not to the elements of the system. It is from these dynamic interrelationships that new properties of the system emerge. In recent years, systems thinking has been developed to provide techniques for studying systems in holistic ways to supplement traditional reductionistic methods. In this more recent tradition, systems theory in organizational studies is considered by some as a humanistic extension of the natural sciences.

Systems theory has also been developed within sociology. An important figure in the sociological systems perspective as developed from GST is Walter Buckley (who from Bertalanffy's theory). Niklas Luhmann (see Luhmann 1994) is also predominant in the literatures for sociology and systems theory. Miller's living systems theory was particularly influential in sociology from the time of the early systems movement. Models for equilibrium in systems analysis that contrasted classical views from Talcott Parsons and George Homas were influential in integrating concepts with the general movement. With the renewed interest in systems theory on the rise since the 1990s, Bailey (1994) notes the concept of systems in sociology dates back to Auguste Comte in the 19th century, Herbert Spencer and Vilfredo Pareto, and that sociology was readying into its centennial as the new systems theory was emerging following the World Wars.

In sociology, members of Research Committee 51 of the International Sociological Association (which focuses on sociocybernetics), have sought to identify the sociocybernetic feedback loops which, it is argued, primarily control the operation of society. On the basis of research largely conducted in the area of education, Raven (1995) has, for example, argued that it is these sociocybernetic processes which consistently undermine well intentioned public action and are currently heading our species, at an exponentially increasing rate, toward extinction. See sustainability. He suggests that an understanding of these systems processes will allow us to generate the kind of (non "common-sense") targeted interventions that are required for things to be otherwise - ie to halt the destruction of the planet.

System Dynamics was founded in the late 1950s by Jay W. Forrester of the MIT Sloan School of Management with the establishment of the MIT System Dynamics Group. At that time, he began applying what he had learned about systems during his work in electrical engineering to everyday kinds of systems.
Determining the exact date of the founding of the field of system dynamics is difficult and involves a certain degree of arbitrariness. Jay W. Forrester joined the faculty of the Sloan School at MIT in 1956, where he then developed what is now System Dynamics. The first published article by Jay W. Forrester in the Harvard Business Review on "Industrial Dynamics", was published in 1958. The members of System Dynamics Society have chosen 1957 to mark the occasion as it is the year in which the work leading to that article, which described the dynamics of a manufacturing supply chain, was done.

As an aspect of systems theory, system dynamics is a method for understanding the dynamic behavior of complex systems. The basis of the method is the recognition that the structure of any system — the many circular, interlocking, sometimes time-delayed relationships among its components — is often just as important in determining its behavior as the individual components themselves. Examples are chaos theory and social dynamics. It is also claimed that, because there are often properties-of-the-whole which cannot be found among the properties-of-the-elements, in some cases the behavior of the whole cannot be explained in terms of the behavior of the parts. An example is the properties of these letters which when considered together can give rise to meaning which does not exist in the letters by themselves. This further explains the integration of tools, like language, as a more parsimoniousprocess in the human application of easiest path adaptability through interconnected systems.

Systems Engineering is an interdisciplinary approach and means for enabling the realization and deployment of successful systems. It can be viewed as the application of engineering techniques to the engineering of systems, as well as the application of a systems approach to engineering efforts.[21] Systems Engineering integrates other disciplines and specialty groups into a team effort, forming a structured development process that proceeds from concept to production to operation and disposal. Systems Engineering considers both the business and the technical needs of all customers, with the goal of providing a quality product that meets the user needs.[22]